I don't regret it at all!!!! So much more space. Still not nearly enough in my opinion though of course.

It's great for the crabs to have more space, but there are challenges. Moved mine into a 120, more on the tall than long side. It's on a stand. I am short, 5'2"-ish, and I had a heck of a time setting it up. Even standing on a chair, I can't reach the bottom of the tank. Even with a foot of substrate, I have issues reaching in.
Second, like wodes said, it's so freakishly heavy! Mine is old and home-made from VERY thick glass and solid wood. Getting it out of somebody's house, into the truck, out of the truck, and then up several steps into my house was a terrible challenge I never want to repeat, even with my 270lb muscly fiance helping! And I'm no weakling myself... It was also raining
hard for all of this, so the tank was slippery. I was convinced we were going to break it before we even got it into the living room. We joke that now we can never move because we can't move the tank again...
We bought a 500lb gun safe after a burglary last year, and THAT WAS SO MUCH EASIER to move into the house than the tank.
And then there are the pools. Mine are about 2 gallons each, and I can't physically lift them out of the tank because of the awkward position I am in reaching that far in. I have to have the fiance do it.
And then there is the matter of all that weight on the floor. The house I live in was built in 1938 by my great grandpa, who was not a construction worker. The floor is doing ok where the 120 is, but I had my 55 in a different part of the living room and the floor is permanently a little saggy there from it. Make sure your floors can take the weight and you turn your tank to be perpendicular with the joists.
Big tanks have their problems, but the crabs are much happier! Totally worth it.

Keep looking for a big one!